The Changing Light at Sandover is Merrill’s grandest achievement. Into its more than five hundred pages has gone everything he knows about writing poetry, everything he believes about living among other people in the world, all his deepest-held values, fears, convictions, and prejudices, spread among passages of “revelation” spelled out on a Quija board. Not everyone will wish, or know how, to approach that sort of book, and not everyone who approaches will feel welcome; the material takes getting used to. But many readers may well feel they have been waiting for this trilogy all their lives.